Last updated: 4/11/2017
Bioelectric navigation (BN) is a new technique for guiding intravascular devices without ionizing radiation. A set of electrodes on the tip of the device creates a small, weak electric field inside the blood vessel. Changes in the geometry of the vessel as the device moves cause measurable changes to the signal at the electrodes. That geometry-dependent signal can be mapped to a previously acquired 3D model of the vessel tree, enabling localization of the device.
The state of the art for intravascular navigation is to first navigate a guidewire under fluoroscopy to the area of interest then advance a catheter over the guidewire. The current BN prototype uses a commercially available, non-irrigated 6F catheter, too large to be used as a guidewire. The goal of this project is to create a guidewire based on the BN technology.
If successful, the guidewire could have a significant impact on minimally invasive endovascular procedures. In the US, there are approximately 8 million endovascular procedures performed every year under fluoroscopic guidance [Schauer and Linton 2009]. Each procedure exposes the patient to the equivalent of 250-3500 chest x-rays [CDRH 2010], so pediatric and pregnant patients are usually unable to benefit from minimally invasive vascular surgery. While BN seems like a promising technology to reduce the dependence on x-ray guidance, its clinical utility is limited by the fact that our prototype is a catheter rather than a guidewire. Our clinical collaborator has specifically asked for a guide wire so that we can test the navigation capabilities of BN in vivo, and the success of this project is integral to the eventual adoption of the technology.
Bold typeface indicates incomplete deliverable.
First, I will research guidewire construction. I found an excellent article outlining how to construct custom guidewires. Next, I’ll simulate a three-electrode guidewire in COMSOL’s electric currents module. I’m interested in how the wire’s signal amplitude compares to the catheter’s. Next, I will design the guidewire. Working with the mentors, I will define the design constraints. I will fully develop at least three designs. The mentors and I will perform a decision analysis to pick the best design. I will improve the embodiment design based on their comments and create the bill of materials. Then I’ll order all of the parts and construct the prototype. Finally, I will test the guidewire in the acrylic phantom. I’ll measure the voltage as the guidewire passes through all six paths of the phantom, using video recordings as ground truth for the guidewire position. I will compare the results to the catheter’s performance in the same phantom. If time allows, I’ll conduct a similar study in a gelatin phantom with x-ray fluoroscopy for ground truth position measurement.
Updated Schedule: https://docs.google.com/spreadsheets/d/1kXa5gIvPE9EK6KhfSXYyZehCjqEUS1cbGhZMy385lno/edit?usp=sharing